An automated BIA2000 optical biosensor is requested as a shared instrument at the University of Pennsylvania. The biosensor is a recently developed technology for quantitative analysis of molecular interaction kinetics. It is applicable to macromolecules and, increasingly, to intermediate-sized biomolecules as well as biological particles such as cells and phage. This technology has been identified as key to the research programs at the University of Pennsylvania, and hence the Biosensor/Interaction Analysis Core Facility was established at the beginning of 1997 to provide a shared biosensor resource to the UPenn research community. The Core Facility currently functions with an IAsys manual biosensor, purchased used in 1996 through joint contributions from the Medical School, the Cancer Center, the Dental School and the College of Arts and Sciences. The used IAsys was bought to investigate utility and overall need of a biosensor at UPenn. As the user base has expanded, an automated, technologically advanced biosensor has become a critical need of University researchers. Major users, and the key research programs they embrace, have formed a User's Group along with other, more minor time-requiring users doing pilot feasibility studies. The BIA2000 is the instrument that most fulfils the demands of the User's Group. The University has made a major commitment to support this shared BIA2000, including space and a funded position for a dedicated operator. The Major Users of the shared BIA2000 will be Irwin Chaiken, Douglas Cines, Charles Clevenger, Gary Cohen/Roselyn Eisenberg, Daniel Malamud and Alan Schreiber. Their projects are focused on three major research problems: (1) Regulation of Kringle-Mediated Fibrinolytic Reactions (Cines), (2) Receptor Interactions and Signalling (Chaiken, Clevenger, Schreiber), and (3) Virus Host Cell Recognition and Viral Entry (Chaiken, Cohen, Malamud). Minor Users doing feasibility studies that will ultimately replenish the Major User's base also will have access to the shared BIA2000. Furthermore, training courses on biosensor technology will be offered to scientists in the UPenn community on an ongoing basis through the Biosensor Core Facility and its Technical Manager, Gabriela Canziani, in order to increase awareness of kinetic study of interaction mechanism using the optical biosensor and to stimulate development of further new projects. Overall, the shared BIA2000 automated biosensor will have far-reaching impact on research in chemistry, biology and medicine at UPenn.